1. Field of the Invention
The present invention relates to an inside micrometer. More specifically, it relates to an inside micrometer with reduced number of components.
2. Description of Related Art
As shown in FIG. 8, a conventional inside micrometer has an inside micrometer body 1 having a first spindle 11 advancing and retracting in accordance with rotation of a thimble 20, a plurality of anvils 30 of mutually different lengths in increments of a predetermined dimension, and an extending collar 40 interposed between the anvil 30 and the inside micrometer body 1.
As shown in FIG. 9, the inside micrometer body 1 has an inner cylinder 2A having a through-hole 3 with an internal thread 4 being formed on the inner circumference thereof adjacent to a first end of the body, an outer cylinder 2B provided on the outer circumference of the inner cylinder 2A, a first spindle 11 composed of a cylindrical first spindle sheath 12 having an external thread 13 screwed to the internal thread 4 of the inner cylinder 2A and a probe 15 screwed to the first end side of the first spindle sheath 12, and a cylindrical thimble 21 covering a part of the inner cylinder 2A and the outer cylinder 2B from the first end to the second end opposite to the first end.
A plurality of slits 3A are formed along cylinder axis of the inner cylinder 2A adjacent to the first end, on which a nut 3B is screwed from the outside. A setscrew 5 having a knob on the head thereof and a support knob 6 are screwed to the outer circumference of the inner cylinder 2A on the second end side.
The outer circumference of the first spindle sheath 12 and an opening 21A of the thimble 21 are fitted on the first end side in a taper 27A of which diameter is increased from the first end side to the second end side, and are clamped by a nut 27B screwed to the probe 15.
A knurl 28 is formed on the outer circumference on the first end side of the thimble 20 and a scale 23 is carved on the outer circumference of the second end side thereof.
The diameter of the first end side of the anvil 30 is the same as the diameter of the through-hole 3 of the inner cylinder 2A on the second end side, which widens at a step 31 on the halfway from the first end side toward the second end side. A probe 32 is provided on the second end side of the anvil 30.
A scale 7 is carved on the outer cylinder 2B in the axial direction of the cylinder.
The extending collar 40 has a through-hole 41 having the same diameter as the first end side of the anvil 30.
In use, one of the anvils 30 of the length suitable for the target portion of the workpiece is selected, which is inserted into the inner cylinder 2A from the second end side and held by the setscrew 5. Subsequently, the thimble 20 of the inside micrometer body 1 is rotated to advance and retract the first spindle 11. When the probe 32 of the anvil 30 and the probe 5 of the first spindle 11 are in contact with the workpiece, the dimension of the target portion of the workpiece is read from the scales 7 and 23.
When the extending collar 40 is used, after the anvil 30 is inserted into the through-hole 41 of the extending collar 40, the anvil 30 is inserted into the inside micrometer body 1. Accordingly, the measurement area of the inside micrometer can be extended for the length of the extending collar 40.
In actual measurement, the anvil 30 and the extending collar 40 are selectively attached to the inside micrometer body 1 according to the workpiece, thereby adjusting the measurement area of the inside micrometer as shown in FIG. 10.
As an instance, it is assumed that the moving distance of the first spindle 11 of the inside micrometer body 1 is 13 mm, the length of the extending collar 40 is 12 mm and two anvils 30 for 50 mm and 75 mm length are prepared.
In order to measure the range for 50 mm to 63 mm, the anvil 30 for 50 mm length is attached to the inside micrometer body 1.
In order to measure the range for 62 mm to 75 mm, the extending collar 40 as well as the anvil 30 for 50 mm length is attached.
In order to measure the range of 75 mm to 88 mm, the anvil 30 for 75 mm length is attached to the inside micrometer body 1.
In the same manner, the anvil 30 and the extending collar 40 are selectively used to extend the measurement area. Accordingly, continuous area can be measured by preparing anvils 30 for different lengths in increments of 25 mm.
However, such a conventional inside micrometer requires anvils 30 of different lengths in increments of 25 mm.
For instance, in order to measure the range from 50 mm to 300 mm, no less than ten anvils 30, i.e. anvils for 50 mm, 75 mm, 100 mm, 125 mm, 150 mm, 175 mm, 200 mm, 225 mm, 250 m and 275 mm lengths, have to be prepared.
According to the above, since the number of components are increased and many number of long anvils 30 have to be prepared, which requires much work and expensive cost. Further, since many number of anvils 30 have to be equipped, the size of accommodation case is increased, which is inconvenient in portable use.
An object of the present invention is to provide an inside micrometer capable of reducing number of components and production cost, and suitable for portable use.
An inside micrometer according to and aspect of the present invention includes: an inside micrometer body including a cylinder having a through-hole, the inner circumference of the through-hole being provided with an internal thread, a first spindle screwed to the internal thread in an advanceable and retractable manner from a first end of the through-hole, and a thimble provided on the outside of the cylinder, the thimble being capable of rotating integrally with the first spindle; a plurality of anvils having different lengths in increments of a predetermined dimension, the anvil being capable of attachment and detachment on the second end opposite to the first end of the through-hole of the cylinder; a first extension member provided with a through-hole to which the anvil is inserted, the first extension member being selectively interposed between the second end side of the cylinder and the anvil to adjust a measurement range; and a second extension member having a second spindle which advances and retracts together with the first spindle, the second extension member being selectively attached to the first end side of the first spindle in an attachable and detachable manner.
According to the above arrangement, when the thimble is rotated, the first spindle rotates together with the thimble. Since the external thread of the first spindle is screwed to the internal thread of the cylinder, the first spindle advances and retracts from the first end side of the cylinder in an axial direction in accordance with the pitch of the screw. The distance for the first spindle to be advanced from the first end side of the cylinder to the outside is the moving distance of the inside micrometer body.
Conventionally, the anvil attached and detached on the second end side of the through-hole of the cylinder and the first extension member interposed between the second end side of the cylinder and the anvil are selectively used to adjust the moving distance of the inside micrometer with the measurement range in accordance with the length of the workpiece.
For instance, when a short anvil is solely used, the measurement range can be set short. When the first extension member is additionally used, the measurement range can be extended by the length of the first extension member. When the anvil is exchanged with a longer one, the measurement range can be further extended, and the measurement range can be adjusted in the same manner.
When the second extension member selectively used together with the anvil and the first extension member is used, following advantages can be obtained.
As described above, after an anvil of a predetermined length is attached to the inside micrometer body and the first extension member is interposed to extend the measurement range, the second extension member is attached to further extend the measurement range.
In other words, the measurement range which can be extended from a single anvil was a sum of the anvil and the length of the first extension member in the conventional arrangement. However, by adding the second extension member, the measurement range can be extended to the sum of the anvil, the first extension member and the second extension member.
Accordingly, the conventionally required length of anvil, i.e. an anvil of the length adding the sum of the length of the first extension member and the second extension member can be omitted.
At this time, the number of the anvils which conventionally required but can be omitted increases in accordance with increase in the length of the measurement range, the above effect becomes further eminent.
A plurality of long anvils can be omitted by the provision of the single second extension member is not only the reduction of components but also is of great importance in reduction of the production cost and the size of the accommodation case in view of the size of the long anvil and manufacturing work thereof.
In the present invention, the relationship of kxe2x89xa6v, sxe2x89xa6v+k, dxe2x89xa6v+k+s may preferably be satisfied, where the moving distance of the first spindle is v, the length of the first extension member is k, the length of the second spindle of the second extension member is s and the increment of the length of the anvil is d.
According to the above arrangement, the measurement range capable of being measured by the inside micrometer can be continuous without gap.
Measurement range S1 of an inside micrometer attached with an anvil A of length a can be represented as: axe2x89xa6S1xe2x89xa6a+v, since the moving distance of the inside micrometer is represented as v.
The measurement range S2 with the anvil A and the first extension member of length k being attached can be represented as: a+kxe2x89xa6S2xe2x89xa6a+k+v. Since kxe2x89xa6v and a+kxe2x89xa6a+v, the relationship of (minimum value of S2)xe2x89xa6(maximum value of S1) is established. Accordingly, S1 and S2 have a crossover range or are continuous.
The measurement range S3 with the anvil A and the second extension member of length s being attached can be represented as: a+sxe2x89xa6S3xe2x89xa6a+s+v. Since sxe2x89xa6k+v and a+sxe2x89xa6a+k+v, the relationship of (minimum value of S3)xe2x89xa6(maximum value of S2) is established. Accordingly, S2 and S3 have a crossover range or are continuous.
The measurement range S4 with the anvil A, the first extension member and the second extension member being attached can be represented as: a+k+sxe2x89xa6S4xe2x89xa6a+k+s+v. Since kxe2x89xa6v and a+k+sxe2x89xa6a+s+v, the relationship of (minimum value of S4)xe2x89xa6(maximum value of S3) is established. Accordingly, S3 and S4 have a crossover range or are continuous.
When the anvil A is exchanged into another anvil having length a+d, the measurement S5 can be represented as: a+dxe2x89xa6S5xe2x89xa6a+d+v. At this time, since dxe2x89xa6v+k+s and a+dxe2x89xa6a+v+k+s, the relationship of (minimum value of S5)xe2x89xa6(maximum value of S4) is established. Accordingly, S4 and S5 have a crossover range or are continuous.
As described above, according to the inside micrometer having the above arrangement, continuous measurement range can be set by a smaller number of anvils as compared to a conventional arrangement.
In the present invention, the second extension member may preferably include: a second extension member body having a through-hole at the center thereof, the second extension member body being attached to the first end side of the thimble in an attachable and detachable manner; a second spindle inserted in an being advanceable and retractable manner from the first end side of the through-hole of the second extension member body in an axial direction; and a biasing means for biasing the second spindle toward the first spindle.
According to the above arrangement, since the position of the second spindle is not fixed in the through-hole of the second extension member but is advanceable and retractable in the axial direction and the second spindle is biased toward the first spindle by the biasing means, when the second extension member is attached to the first end side of the thimble, the first end of the first spindle and the second end of the second spindle are in contact with each other, so that the second end of the second spindle is pushed by the first end of the first spindle, thereby slidably moving the second spindle toward the first end side. Accordingly, the effect equal to adding the length of the second spindle to the first spindle can be attained, thereby effectively working as an extension member.
At this time, even when the length for the first spindle to project from the cylinder of the inside micrometer body changes, the position of the second spindle is flexibly changed and the second spindle can be touched to the first end of the first spindle without generating gap. In other words, since the first and the second spindles are integrally advanced and retracted, the measurement accuracy is not deteriorated.
In the present invention, an external thread may preferably be formed on one of the second end side of the second extension member and the first end side of the thimble, and an internal thread to be screwed to the external thread may preferably be formed on the other of the second end side of the second extension member and the first end side of the thimble.
According to the above arrangement, since the second extension member moves integrally with the thimble by screwing the first end side of the thimble and the second end side of the second extension member, the second extension member moves together with the first spindle when the thimble moves with the first spindle by rotating the thimble, thereby effectively working as an extension member.
Further, since the thimble and the second extension are screwed and therefore are easily attached and detached, portability can be improved and, since any one of the thimble and the second extension member may be rotated, operability can also be enhanced.